1. Field of the Invention
The present invention relates generally to magnetic sensing systems, and more specifically, to a magnetic sensing system for outputting a plurality of voltage or current signals in digital form as a collective representation of any incremental rotational, linear, or pivotal movement of an object.
2. Background
Magnetic sensors known in the art are operable to output an analog signal as a function of the magnetic flux density of any magnetic flux passing through one or more magnetic flux sensitive transducers of the magnetic sensor, e.g. a magneto-resistor, a Hall effect element, a coil, etc. The magnetic sensor is spatially positioned from an object to define an air gap area therebetween. A portion of a magnetic field traverses the air gap area, and the magnetic flux sensitive transducer(s) is (are) disposed within the magnetic field. As a result, the magnitude of the analog signal varies in response to any rotational movement, any linear movement, and/or any pivotal movement of the object that increases or decreases the reluctance across the air gap area to thereby alter the magnetic flux density of the magnetic flux passing through the magnetic flux sensitive transducer(s). Consequently, whenever any cyclical movement of the object undulates any magnetic flux passing through the magnetic flux sensitive transducer(s), each incremental movement of the object away from a reference position of the object is represented by a particular magnitude of the analog signal. Accordingly, the analog signal of a magnetic sensor has been and will continue to be extensively utilized by various electromechanical systems to ascertain a present position of the object relative to a reference position of the object.
Particularly, magnetic rotational position sensors have been extensively incorporated in engine timing systems of motor vehicles to ascertain the present rotational position of a rotary shaft relative to a reference position of the rotary shaft. Typically, the magnitude level of the analog signal is representative of a present rotational position of the rotary shaft relative to a reference position of the rotary shaft. For example, a magnitude of zero (0) volts can represent a closed position of the shaft. a magnitude of five (5) volts can represent a completely opened position of the rotary shaft that is a ninety (90) degree range of rotation from the closed position, and each magnitude of the analog signal between zero (0) volts and five (5) volts is linearly representative of a particular degree of rotation of the rotary shaft from the closed position. A computer of the motor vehicle therefore includes some form of xe2x80x9clookupxe2x80x9d table to ascertain the present rotational position of the rotary shaft relative to the closed position as a function of the magnitude of the analog signal. Thus, if the computer receives the analog signal with a magnitude of 2.5 volts, the computer can ascertain that the rotary shaft is forty-five (45) degrees from the closed position based on the lookup table.
However, in some cases, it is desired to ascertain a degree of a rotational movement of a rotary shaft between two rotational positions, and in such cases, the present magnitude of the analog signal is not a representation of the degree of rotational movement of a rotary shaft between the two rotational positions. In order to ascertain the degree of rotational movement of the rotary shaft between the two rotational positions, the computer would have to be programmed to: (1) ascertain the initial rotational position of the rotary shaft relative to the reference position of the rotary shaft; (2) ascertain the present rotational position of the rotary shaft relative to the reference position of the rotary shaft; (3) determine the difference between the magnitude of the analog signal when the rotary shaft was at its initial rotational position and the present magnitude of the analog signal; and (4) ascertain the degree of movement as a function of the differences in the magnitudes. It is clear that this would require ample memory space and an appropriate clock signal to allow each of the calculations to be completed in a timely manner. However, the memory space may not be available, and/or the clock signal may be running at a frequency that will not enable the completions of the calculations in a timely manner. What is therefore needed is a system for ascertaining a degree of rotational, linear, or pivotal movement of an object between two positions.
The present invention overcomes the aforementioned drawback(s) associated with magnetic position sensors in ascertaining a degree of movement of an object. Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention described in detail herein can only be determined with reference to the claims appended hereto, certain features which are characteristic of the present invention disclosed herein can be described briefly.
The present invention is a magnetic incremental motion detection system for outputting a plurality of voltage and/or current signals in digital form wherein the voltage and/or current signals are a collective representation of any incremental rotational, linear, or pivotal movement of an object. A target of the system is adjoined to an object to synchronously move with the object. A plurality of indications are adjoined to the target, and uniformly and serially disposed along an area of a surface of the target.
In a first aspect of the present invention, a pair of magnetic sensing devices of the system are spatially positioned from the area of the surface to define air gap area(s) therebetween. Each magnetic sensing device includes a magnetic sensor and a digital circuit having a signal amplification stage and a signal comparison stage. Each magnetic sensing device is operable to output a digital signal in response to a synchronous movement of the target with the object. The outputted digital signals have identical duty cycles, and are consistently out of phase with each other by the same degree.
In a second aspect of the present invention, a magnetic sensing device of the system is spatially positioned from the area of the surface to define an air gap area therebetween. The magnetic sensing device includes a magnetic sensor and pair of digital circuits each having a signal amplification stage and a signal comparison stage. The magnetic sensing device is operable to output a pair of digital signals in response to a synchronous movement of the target with the object. The outputted digital signals have identical duty cycles, and are consistently out of phase with each other by the same degree.
It is a primary objective of the present invention to sense each incremental rotational, linear, or pivotal movement of an object.
It is also a primary objective of the present invention to a plurality of voltage or current signals in digital form as a collective representation of each sensed incremental rotational, linear, or pivotal movement of an object.
Secondary objectives as well as advantages of the present invention will be apparent from the following description of the present invention and various embodiments thereof.